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Glossary
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Crystal Bulks
autodoping – dopant, from sources other than the dopant intentionally added to the vapor phase, which is incorporated into an epitaxial layer during growth.
autodoping barrier – a film or layer which impedes transport of impurity atoms from the back surface of a substrate to the epi layer during epitaxial deposition. Also known as backseal.
conductivity type – defines the nature of the majority of the carriers in silicon: n-type material, in which electrons are the majority carrier, is formed when a donor dopant impurity is added to the silicon; p-type material, in which holes are the majority carrier, is formed when an acceptor dopant impurity is added to the silicon.
crystal orientation – the crystallographic axis, on which the silicon crystal is grown. In generally supplied in <100> or <111> orientations.
dislocation – a line imperfection in a crystal which forms the boundary between slipped and nonslipped regions of the crystal.
dislocation density – the number of dislocation etch pits per unit area on an exposed wafer surface.
dislocation etch pit – a sharply defined depression in the immediate region of a stressed or defective crystal lattice, resulting from preferential etching.
dopant – a chemical element from the third (such as boron) or fifth (such as phosphorus or antimony) column of the periodic table, intentionally incorporated into a silicon crystal in trance amounts to establish its conductivity type and resistivity.
P-Type
Bor 0,001 – 50 ohmcm
N-Type
Phosphorus 0,1 – 40 ohmcm
Antimony 0,005 – 0,025 ohmcm
Arsenic < 0,005 ohmcm
extrinsic gettering – controlled damage or stress to the crystal lattice structure intentionally introduced by mechanical means or by deposition of a polysilicon or other film on the back surface of a silicon wafer.
flat orientation (primary) – the crystallographic plane, which ideally coincides with the surface of the primary flat, The primary flat is usually a <110> plane.
Miller indices – the reciprocals of the intercepts of a crystallographic plane with the x-, y-, and z-axes, respectively. For example, the cube face perpendicular to the x-axis is the <100> plane. A family of planes is denoted by curly brackets; e.g., all cube faces are the <100> planes. Directions are denoted by Miller indices in square brackets; e.g., the x-axis is the <100> direction an the cube diagonal is the <111> direction. Families of directions are denoted by angular brackets; e.g., all cubic axes are the <100> directions. A negative direction is denoted by a minus sign over the index; e.g., the negative x-axis is the <¯100> direction.
polycrystalline silicon (polisilicon, poly) – silicon made up of randomly oriented crystallites and containing large-angle grain boundaries, twin boundaries, or both.
radial oxygen variation – the difference between the average oxygen concentration at one or more points symmetrically located on a silicon wafer and the oxygen concentration at the center of the wafer, expressed as a percent of the concentration at the center. Unless otherwise specified, Siltec considers the radial oxygen variation to be determined using the average of the oxygen concentrations at the two points 10 mm from the edge of the wafer. Radial oxygen variation is sometimes determined using the average of the oxygen concentrations at several symmetric points half way between the center and the edge of the wafer . Also known as oxygen gradient.
radial resistivity variation – the difference between the average resistivity at one or more points symmetrically located on a silicon wafer and the resistivity at the center of the wafer, expressed as a percent of the resistivity at the center, Unless otherwise specified, we consider the radial resistivity variation to be determined using the average resistivity of four points 6 mm from the edge of the wafer on two perpendicular diameters. Radial resistivity variation is sometimes determined using the average of the resistivity at the four point half way between the center and the edge of the wafer on the same diameters. Also known as resistivity gradient.
resistivity (ohm·cm) – the ratio of the potential gradient (electric field) parallel with the current to the current density, In silicon, the resistivity is controlled by adding dopant impurities; lower resistivity is achieved by adding more dopant.
slip – a process of plastic deformation in which one part of a crystal undergoes a shear displacement relative to another in a fashion which preserves the crystallinity of the silicon. After preferential etching, slip is evidenced by a pattern of one or more parallel straight lines of 10 or more dislocation etch pits per millimeter which do not necessarily toch each other. On <111> surfaces, groups of lines are inclined at 60º to each other; on <100> surfaces, they are inclined at 90º to each other.
stacking fault – a two-dimensional defect resulting from a deviation from the normal stacking sequence of atoms in a crystal. It may be present in the bulk crystal, grow during epitaxial deposition (usually as a result of a contaminated or structurally imperfect substrate surface); or develop during oxydation. On <111> surfaces, stacking faults are revealed by preferential etching either as closed or partial equilateral triangles. On <100> surfaces, stacking faults are revealed as closed or partial squares.
striations – helical features on the surface of a silicon wafer associated with local variations in impurity concentration. Such variations are ascribed to periodic differences in dopant incorporation occurring at the rotating solid-liquid interface during crystal growth. Striations are visible to the unaided eye after preferential etching and appear to be continuous under 100X magnification.
subsurface damage – residual crystallographic imperfections apparent only after preferential etching of the polished silicon surface. Such damage is usually considered to be caused by mechanical processing of the wafer.
twinned crystal – a crystal in which the lattice consists of two parts related to each other in orientation as mirror images across a coherent planar interface known as the twinning plane or twin boundary, In silicon, this plane is a <111> plane. Also known as twin.
wafer orientation – the crystallographic plane, described in terms of Miller indices, with which the surface of the wafer is ideally coincident. Generally, the surface of the wafer corresponds within a few degrees with the low index plane perpendicular to the growth axis. In such cases, the orientation may also be described in terms of the angular deviation a of the low-index crystallographic plane from the polished wafer surface.
Crystal Bulks
autodoping – dopant, from sources other than the dopant intentionally added to the vapor phase, which is incorporated into an epitaxial layer during growth.
autodoping barrier – a film or layer which impedes transport of impurity atoms from the back surface of a substrate to the epi layer during epitaxial deposition. Also known as backseal.
conductivity type – defines the nature of the majority of the carriers in silicon: n-type material, in which electrons are the majority carrier, is formed when a donor dopant impurity is added to the silicon; p-type material, in which holes are the majority carrier, is formed when an acceptor dopant impurity is added to the silicon.
crystal orientation – the crystallographic axis, on which the silicon crystal is grown. In generally supplied in <100> or <111> orientations.
dislocation – a line imperfection in a crystal which forms the boundary between slipped and nonslipped regions of the crystal.
dislocation density – the number of dislocation etch pits per unit area on an exposed wafer surface.
dislocation etch pit – a sharply defined depression in the immediate region of a stressed or defective crystal lattice, resulting from preferential etching.
dopant – a chemical element from the third (such as boron) or fifth (such as phosphorus or antimony) column of the periodic table, intentionally incorporated into a silicon crystal in trance amounts to establish its conductivity type and resistivity.
P-Type
Bor 0,001 – 50 ohmcm
N-Type
Phosphorus 0,1 – 40 ohmcm
Antimony 0,005 – 0,025 ohmcm
Arsenic < 0,005 ohmcm
extrinsic gettering – controlled damage or stress to the crystal lattice structure intentionally introduced by mechanical means or by deposition of a polysilicon or other film on the back surface of a silicon wafer.
flat orientation (primary) – the crystallographic plane, which ideally coincides with the surface of the primary flat, The primary flat is usually a <110> plane.
Miller indices – the reciprocals of the intercepts of a crystallographic plane with the x-, y-, and z-axes, respectively. For example, the cube face perpendicular to the x-axis is the <100> plane. A family of planes is denoted by curly brackets; e.g., all cube faces are the <100> planes. Directions are denoted by Miller indices in square brackets; e.g., the x-axis is the <100> direction an the cube diagonal is the <111> direction. Families of directions are denoted by angular brackets; e.g., all cubic axes are the <100> directions. A negative direction is denoted by a minus sign over the index; e.g., the negative x-axis is the <¯100> direction.
polycrystalline silicon (polisilicon, poly) – silicon made up of randomly oriented crystallites and containing large-angle grain boundaries, twin boundaries, or both.
radial oxygen variation – the difference between the average oxygen concentration at one or more points symmetrically located on a silicon wafer and the oxygen concentration at the center of the wafer, expressed as a percent of the concentration at the center. Unless otherwise specified, Siltec considers the radial oxygen variation to be determined using the average of the oxygen concentrations at the two points 10 mm from the edge of the wafer. Radial oxygen variation is sometimes determined using the average of the oxygen concentrations at several symmetric points half way between the center and the edge of the wafer . Also known as oxygen gradient.
radial resistivity variation – the difference between the average resistivity at one or more points symmetrically located on a silicon wafer and the resistivity at the center of the wafer, expressed as a percent of the resistivity at the center, Unless otherwise specified, we consider the radial resistivity variation to be determined using the average resistivity of four points 6 mm from the edge of the wafer on two perpendicular diameters. Radial resistivity variation is sometimes determined using the average of the resistivity at the four point half way between the center and the edge of the wafer on the same diameters. Also known as resistivity gradient.
resistivity (ohm·cm) – the ratio of the potential gradient (electric field) parallel with the current to the current density, In silicon, the resistivity is controlled by adding dopant impurities; lower resistivity is achieved by adding more dopant.
slip – a process of plastic deformation in which one part of a crystal undergoes a shear displacement relative to another in a fashion which preserves the crystallinity of the silicon. After preferential etching, slip is evidenced by a pattern of one or more parallel straight lines of 10 or more dislocation etch pits per millimeter which do not necessarily toch each other. On <111> surfaces, groups of lines are inclined at 60º to each other; on <100> surfaces, they are inclined at 90º to each other.
stacking fault – a two-dimensional defect resulting from a deviation from the normal stacking sequence of atoms in a crystal. It may be present in the bulk crystal, grow during epitaxial deposition (usually as a result of a contaminated or structurally imperfect substrate surface); or develop during oxydation. On <111> surfaces, stacking faults are revealed by preferential etching either as closed or partial equilateral triangles. On <100> surfaces, stacking faults are revealed as closed or partial squares.
striations – helical features on the surface of a silicon wafer associated with local variations in impurity concentration. Such variations are ascribed to periodic differences in dopant incorporation occurring at the rotating solid-liquid interface during crystal growth. Striations are visible to the unaided eye after preferential etching and appear to be continuous under 100X magnification.
subsurface damage – residual crystallographic imperfections apparent only after preferential etching of the polished silicon surface. Such damage is usually considered to be caused by mechanical processing of the wafer.
twinned crystal – a crystal in which the lattice consists of two parts related to each other in orientation as mirror images across a coherent planar interface known as the twinning plane or twin boundary, In silicon, this plane is a <111> plane. Also known as twin.
wafer orientation – the crystallographic plane, described in terms of Miller indices, with which the surface of the wafer is ideally coincident. Generally, the surface of the wafer corresponds within a few degrees with the low index plane perpendicular to the growth axis. In such cases, the orientation may also be described in terms of the angular deviation a of the low-index crystallographic plane from the polished wafer surface.
Polished Wafers
bow – a measure of concave or convex deformation of the median surface of a wafer, independent of any thickness variation which may be present. Bow is determined at the center point of the wafer with respect to a reference plane determined by three points equally spaced on a circle whose diameter is 6.35 mm less than the nominal wafer diameter. Bow is a bulk property of the wafer, not a property of an exposed surface. Generally, bow is determined with the wafer in a free, unclamped position. (Not to be confused with warp.)
diameter – the linear distance across a circular silicon wafer which includes the wafer center and excludes any flats or other peripheral fiducial areas.
edge contour – the cross sectional profile of a wafer edge shaped by grinding or etching. Edges may be either rounded or bevelled.
flatness – for wafer surfaces, the deviation of the front surface, expressed as TIR or maximum FPD, relative to a specified reference plane when the back surface of the wafer is ideally flat, as when pulled down by vacuum onto an ideally clean flat chuck. The flatness of a wafer may be described as;
1. the global flatness, or
2. the maximum value of site flatness as measured on all sites, or
3. the percentage of sites which have a site flatness equal to or less than a specified value.
flatness qualitiy area – that portion of the surface of a wafer over which the specified flatness values apply. The flatness qualitiy area is most frequently defined with an edge exclusion area, a peripheral annulus usually 3 mm wide.
focal plane – the plane perpendicular to the optical axis of an imaging system which contains the focal point of the imaging system.
focal plane deviation (FPD) – the distance parallel to the optical axis from a point on the wafer surface to the focal plane.
global flatness – the TIR or maximum FPD within the flatness quality area relative to a specified reference plane.
maximum FPD – the largest of the absolute values of the focal plane deviations.
primary flat – the flat of longest length which is oriented with respect to a specific crystallographic plane. Also known as major flat.
reference plane – a plane specified by one of the following:
1. three points at specified locations on the front surface of the wafer, or
2. the least squares fit to the front surface of the wafer using all points within the flasness quality area, or
3. the least squares fit to the front surface of the wafer using all points within a site, or
4. an ideal back surface (equivalent to the ideally flat chuck surface that contacts the wafer).
secondary flat(s) – the flat or flats of a length shorter than that of the primary flat whose angular position with respect to the primary flat identifies the conductivity type and orientation of the wafer. Also known as minor flat.
site – a rectangular area, on the front surface of the wafer, whose sides are parallel with and perpendicular to the primary flat and whose center falls within the flatness quality area.
site flatness – the TIR or maximum FPD of the portion of a site which falls within the flatness quality area.
thickness – the distance through the wafer between corresponding points on the front and back surface.
total indicator reading (TIR) – the smallest perpendicular distance between two planes, both parallel with the reference plane, which enclose all points within a specified flatness quality area or site on the front surface of a wafer.
total thickness variation (TTV) – the difference between the maximum and minimum thickness values encountered during a scan pattern or a series of point measurements on a wafer.
warp – the difference between the maximum and minimum distances of the median surface of the wafer from a reference plane encountered during a scan pattern. Warp is a bulk property of the wafer, not a property of an exposed surface. The median surface may contain regions with upward or downward curvature or both. Generally, warp is determined with the wafer in a free, umclamped position. (Not to be confused with bow.)
Polished Wafers
bow – a measure of concave or convex deformation of the median surface of a wafer, independent of any thickness variation which may be present. Bow is determined at the center point of the wafer with respect to a reference plane determined by three points equally spaced on a circle whose diameter is 6.35 mm less than the nominal wafer diameter. Bow is a bulk property of the wafer, not a property of an exposed surface. Generally, bow is determined with the wafer in a free, unclamped position. (Not to be confused with warp.)
diameter – the linear distance across a circular silicon wafer which includes the wafer center and excludes any flats or other peripheral fiducial areas.
edge contour – the cross sectional profile of a wafer edge shaped by grinding or etching. Edges may be either rounded or bevelled.
flatness – for wafer surfaces, the deviation of the front surface, expressed as TIR or maximum FPD, relative to a specified reference plane when the back surface of the wafer is ideally flat, as when pulled down by vacuum onto an ideally clean flat chuck. The flatness of a wafer may be described as;
1. the global flatness, or
2. the maximum value of site flatness as measured on all sites, or
3. the percentage of sites which have a site flatness equal to or less than a specified value.
flatness qualitiy area – that portion of the surface of a wafer over which the specified flatness values apply. The flatness qualitiy area is most frequently defined with an edge exclusion area, a peripheral annulus usually 3 mm wide.
focal plane – the plane perpendicular to the optical axis of an imaging system which contains the focal point of the imaging system.
focal plane deviation (FPD) – the distance parallel to the optical axis from a point on the wafer surface to the focal plane.
global flatness – the TIR or maximum FPD within the flatness quality area relative to a specified reference plane.
maximum FPD – the largest of the absolute values of the focal plane deviations.
primary flat – the flat of longest length which is oriented with respect to a specific crystallographic plane. Also known as major flat.
reference plane – a plane specified by one of the following:
1. three points at specified locations on the front surface of the wafer, or
2. the least squares fit to the front surface of the wafer using all points within the flasness quality area, or
3. the least squares fit to the front surface of the wafer using all points within a site, or
4. an ideal back surface (equivalent to the ideally flat chuck surface that contacts the wafer).
secondary flat(s) – the flat or flats of a length shorter than that of the primary flat whose angular position with respect to the primary flat identifies the conductivity type and orientation of the wafer. Also known as minor flat.
site – a rectangular area, on the front surface of the wafer, whose sides are parallel with and perpendicular to the primary flat and whose center falls within the flatness quality area.
site flatness – the TIR or maximum FPD of the portion of a site which falls within the flatness quality area.
thickness – the distance through the wafer between corresponding points on the front and back surface.
total indicator reading (TIR) – the smallest perpendicular distance between two planes, both parallel with the reference plane, which enclose all points within a specified flatness quality area or site on the front surface of a wafer.
total thickness variation (TTV) – the difference between the maximum and minimum thickness values encountered during a scan pattern or a series of point measurements on a wafer.
warp – the difference between the maximum and minimum distances of the median surface of the wafer from a reference plane encountered during a scan pattern. Warp is a bulk property of the wafer, not a property of an exposed surface. The median surface may contain regions with upward or downward curvature or both. Generally, warp is determined with the wafer in a free, umclamped position. (Not to be confused with bow.)
Surface Defects
chip – region where material has been removed from the surface or edge of the wafer. The size of a chip is defined by its maximum radial depth and peripheral chord length as measured on an orthographic shadow projection of the specimen outline. Also known as clamshell, conchoidal fracture, edge chip, flake, nick, peripheral chip, peripheral indent, and surface chip.
contamination – a broad category of foreign matter visible to the unaided eye on the wafer surface. In most cases, it is removable by gas blow off, detergent wash, or chemical action. See also particulate contamination, stain.
crack – cleavage that extends to the surface of a wafer and which may or may not pass through the entire thickness of the wafer. Also known as fissure; see also fracture.
cratering – a surface texture of irregular closed ridges with smooth central regions.
crow’s-foot – intersecting cracks in a pattern resembling a “crow`s foot” (Y) on <111> surfaces and a cross (+) on <100> surfaces.
dimple – a smooth surface depression, larger than 3 mm in diameter, on a wafer surface.
fracture – a crack with single or multiple lines radiating from a point.
groove – a shallow scratch with rounded edges, usually the remnant of a scratch not completely removed during polishing.
haze – a cloudy or hazy appearance attributable to light scattering by concentrations of microscopic surface irregularities such as pits, mounds, small ridges or scratches, particles, etc.
imbedded abrasive grains – abrasive particles mechanically forced into the surface of the silicon wafer. This type of contamination may occur during slicing, lapping, or polishing.
indent – an edge defect that extends from the front surface to the back surface of the silicon wafer.
light point defects (LPD) – individual fine points of reflected light seen when the wafer is illuminated by a narrow-beam light source held perpendicular to the wafer surface.
mound – irregularly shaped projection with one or more facets. Mounds can be extensions of the bulk material or various forms of contamination, or both. A high density of mounds can also appear as haze.
orange peel – a large-featured, roughened surface, similar to the skin of an orange, visible to the unaided eye under fluorescent light but not usually under narrow-beam illumination.
particulate contamination – a form of contamination comprising particles, such as dust, lint, or other material resting on the surface of the wafer and standing out from the surface. May usually be blown off the surface with clean, dry nitrogen.
pit – a depression in the surface where the sloped sides of the depression meet the wafer surface in a distinguishable manner (in contrast to the rounded sides of a dimple).
saw blade defect – a roughened area visible after polishing with a pattern characteristic of the saw blade travel. It may be descernible before chemical polishing. Also known as saw mark.
scratch – a shallow groove or cut below the established plane of the surface, with a length-to-width ratio greater than 5:1. A macroscratch is =0.12µm in depth and is visible to the unaided eye under both incandescent (narrow-beam) and fluorescent illumination. A microscratch is <0.12µm in depth and is not visible to the unaided eye under flourescent illumination.
spike – a tall, thin dendrite or crystalline filament which often occurs at the center of a recess in the surface of an epitaxial layer.
stain – a form of contamination such as a streak, smudge, or spot which contains foreign chemical compounds such as organics or salts.
Surface Defects
chip – region where material has been removed from the surface or edge of the wafer. The size of a chip is defined by its maximum radial depth and peripheral chord length as measured on an orthographic shadow projection of the specimen outline. Also known as clamshell, conchoidal fracture, edge chip, flake, nick, peripheral chip, peripheral indent, and surface chip.
contamination – a broad category of foreign matter visible to the unaided eye on the wafer surface. In most cases, it is removable by gas blow off, detergent wash, or chemical action. See also particulate contamination, stain.
crack – cleavage that extends to the surface of a wafer and which may or may not pass through the entire thickness of the wafer. Also known as fissure; see also fracture.
cratering – a surface texture of irregular closed ridges with smooth central regions.
crow’s-foot – intersecting cracks in a pattern resembling a “crow`s foot” (Y) on <111> surfaces and a cross (+) on <100> surfaces.
dimple – a smooth surface depression, larger than 3 mm in diameter, on a wafer surface.
fracture – a crack with single or multiple lines radiating from a point.
groove – a shallow scratch with rounded edges, usually the remnant of a scratch not completely removed during polishing.
haze – a cloudy or hazy appearance attributable to light scattering by concentrations of microscopic surface irregularities such as pits, mounds, small ridges or scratches, particles, etc.
imbedded abrasive grains – abrasive particles mechanically forced into the surface of the silicon wafer. This type of contamination may occur during slicing, lapping, or polishing.
indent – an edge defect that extends from the front surface to the back surface of the silicon wafer.
light point defects (LPD) – individual fine points of reflected light seen when the wafer is illuminated by a narrow-beam light source held perpendicular to the wafer surface.
mound – irregularly shaped projection with one or more facets. Mounds can be extensions of the bulk material or various forms of contamination, or both. A high density of mounds can also appear as haze.
orange peel – a large-featured, roughened surface, similar to the skin of an orange, visible to the unaided eye under fluorescent light but not usually under narrow-beam illumination.
particulate contamination – a form of contamination comprising particles, such as dust, lint, or other material resting on the surface of the wafer and standing out from the surface. May usually be blown off the surface with clean, dry nitrogen.
pit – a depression in the surface where the sloped sides of the depression meet the wafer surface in a distinguishable manner (in contrast to the rounded sides of a dimple).
saw blade defect – a roughened area visible after polishing with a pattern characteristic of the saw blade travel. It may be descernible before chemical polishing. Also known as saw mark.
scratch – a shallow groove or cut below the established plane of the surface, with a length-to-width ratio greater than 5:1. A macroscratch is =0.12µm in depth and is visible to the unaided eye under both incandescent (narrow-beam) and fluorescent illumination. A microscratch is <0.12µm in depth and is not visible to the unaided eye under flourescent illumination.
spike – a tall, thin dendrite or crystalline filament which often occurs at the center of a recess in the surface of an epitaxial layer.
stain – a form of contamination such as a streak, smudge, or spot which contains foreign chemical compounds such as organics or salts.